For the past few years, we have been interested in establishing conditions for the study of the components necessary for correct in vitro synthesis of specific RNA molecules. We have established a procedure for the isolation of DNA dependent RNA polymerase from nuclei of BSC-1 cells in culture. These cells are permissive to infection by the transforming virus SV40. We have begun experiments to analyze the transcription of SV40 DNA-protein complexes by relatively crude preparations of RNA polymerase isolated from cells infected with SV40. We have found that under certain conditions, we can achieve asymmetric transcription of the SV40 DNA-protein complexes such that the correct strand from both the early and late regions of the virus are used by the enzyme. Current studies are directed towards determining components necessary for proper strand selection.